The invention relates to a system for determining the angular spin position of a second object spinning about an axis with respect to a first object. The invention also relates to a first and a second object, which are suitable for use in said system. Such a system is of prior art regarding the second object, where a position indicator fitted thereon can clearly be localised on the second object. Hence, this usually concerns objects located in the direct vicinity of the first object (the measuring position). Such a system however cannot be applied to a remote second object, as a position indicator fitted thereon can no longer be localised from the measuring position. In case of fired projectiles, such as shells, it is often desirable to change the course during the flight. However, since a shell spins about its axis along the trajectory, correction of its course is effective only if at any random instant the associated spin or roll position is well-known. Suitable course correction means for this purpose are preferably based on principles of the aerodynamics, the chemistry, the gas theory and the dynamics. In this respect, considered are the bringing out of damping fins or surfaces on the projectile's circumferential surface, the detonation of small charges on the projectile, and the ejection of a small mass of gas from the projectile.